The present invention relates to a production of plastic products through a molding process and, more particularly, to a plastic product having desired thermal insulation property, desired light transmitting effect, desired buoyancy, and desired durability, and to a method and device for producing such plastic products by extruding a melted plastic material to form a plastic structural body, and sequentially blowing, filling and molding the structural body before the hardening of the body to produce resulting plastic products.
In a conventional extrusion molding process, plastic material is melted at a predetermined temperature to become a half-melted gel. The half-melted plastic material is, thereafter, fed to an extrusion head by means of a feeding unit, such as a feed screw, and so a plastic structural body having an outer shape determined by the shape of a dice mold provided in the extrusion head is produced.
A conventional extrusion-molding device for performing such an extrusion molding process comprises a plurality of cores provided in the housing of an extrusion head. A dice mold, having a shape corresponding to a desired shape of resulting products, is set in the terminal of the housing. A water-cooling unit is provided outside the extrusion head for cooling the structural body discharged from the dice mold.
In a conventional extrusion molding process using such a conventional extrusion-molding machine, the shape of the resulting products is determined by the dice mold when the melted plastic material passes through the dice mold. In such a case, a plastic structural body is discharged from the dice mold while being initially cooled by a primary cooling unit provided around the dice mold, and is then cooled by a water-cooling unit longitudinally installed along a feeding passage extending from the dice mold. The structural body is, thereafter, cut by a cutter installed at the terminal of the passage.
The above-mentioned conventional extrusion molding process has been preferably used to form a variety of plastic products having the same cross-section, such as wires, rods and panels. As the plastic products produced by the conventional extrusion molding process are hollow members, they are preferably lightweight. However, the plastic products may be undesirably weak in their structure for an impact, particularly when they have thin walls.
In addition, the extrusion-molded plastic products are produced by cutting a linear structural body, and so each product has cut surfaces at both end surfaces of the product, with a cavity longitudinally formed in inner-space of each product. The longitudinal cavity has to been opened at both end portions.
A conventional extrusion molding process of producing such plastic products comprises the steps of: melting a plastic material; extruding the melted plastic material to feed the plastic material into a molding cavity defined by the housing and cores of an extrusion head; shaping a plastic structural body by extruding the plastic material through a dice mold installed at the terminal of the extrusion head housing; initially cooling the plastic structural body by a primary cooling unit provided around the dice mold; then cooling the structural body by a water cooling unit longitudinally installed along a feeding passage extending from the dice mold; and cutting the plastic structural body by a cutter installed at the terminal of the passage. Therefore, it is impossible to produce plastic products having shapes different from that of the dice mold through a conventional extrusion molding process.
A variety of plastic products, each having a completely sealed and completely continuous sidewall, a sealed cavity defined within the sidewall, and a shaping part having a desired shape and formed in the cavity, are preferably usable for a variety of applications in a variety of industrial fields. However, it is impossible to produce such plastic products through a conventional extrusion molding process or a conventional injection molding process.
In a conventional injection molding process, melted plastic material heated to a predetermined temperature is injected into a cavity defined between the open able top and bottom molds of an injection-molding machine. After the product is hardened, the top mold is separated from the bottom mold prior to ejecting the product from the cavity using an ejection unit. Therefore, the plastic products produced through a conventional injection molding process do not have a sealed cavity, but are open in their structures in the direction of mold opening.
In addition, even though plastic products are produced through a conventional injection molding process with a variety of cores, it is impossible to form a desired shaping part, such as a rib, in the cavity of the products.
It is also impossible to produce the above-mentioned plastic products, each having a completely sealed and completely continuous sidewall, a sealed cavity defined within the sidewall, and a shaping part having a desired shape and formed in the cavity, through another conventional forming process, such as a blow molding process or a vacuum forming process which is used for producing tubes, containers or a variety of casings in the prior art.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a plastic product, which each have a completely sealed and completely continuous sidewall, at least one sealed cavity having a single or multi-layered structure and defined within the sidewall, and a shaping part having a desired shape and formed in the cavity.
Another object of the present invention is to provide a plastic product, which has an air suction valve and an air exhaust valve on its sidewall to perform a respiration action through the valves in response to thermal expansion or contraction of a sealed cavity inside the sidewall, thus being protected from undesired deformation or breakage regardless of a change in atmospheric temperature.
A further object of the present invention is to provide a plastic product, which has an integrated structure having filler, such as urethane filler, welded to a sealed cavity of a plastic structural body of the product.
Still another object of the present invention is to provide an extrusion molding method and device, which produces a plastic product through a continuous blow molding process and/or a mold forming process, the product consisting of a plastic structural body having a completely sealed sidewall, with a plurality of ribs formed on the sidewall to form a plurality of cavities in the structural body;
Another object of the present invention is to provide an extrusion molding method and device, which produces a plastic product through a filling process, in addition to a continuous blow molding process and/or a mold forming process, the product consisting of a plastic structural body having a completely sealed sidewall, with a plurality of ribs formed on the sidewall to form a plurality of cavities in the structural body, and a filler integrally filling each of the cavities;
Another object of the present invention is to provide an extrusion molding method and device, which produces a plastic product by continuously injecting a filler, such as resin foam, into the cavity of a plastic structural body of the product while forming the product, thus integrating the filler with the sidewall of the product.
Another object of the present invention is to provide plastic products including panel type, pipe type, channel type, door panel type, boat type, and column type having a specifically designed structure with a completely sealed and completely continuous sidewall and at least one sealed cavity defined inside the sidewall, thus having desired thermal insulation property, desired no flammability, desired light transmitting effect, desired buoyancy, desired durability; being preferably usable as interior or exterior materials in a variety of applications, such as automobiles, ships, airplanes, buildings, structural frames, and other industrial applications; and to provide an extrusion molding method and device for producing such plastic products through a continued process in commercial quantity.
In order to accomplish the above object, the present invention provides a plastic product of the panel type, boat type, column type, beam type, channel type or other structural frame type, comprising: a plastic structural body formed through an extrusion molding process, a blow molding process and/or a mold-forming process, and having a sealed sidewall defining one or more sealed cavities therein to form a single- or multi-layered cavity structure.
In present invention, said sidewall may have a single-, double-, triple-, or multi-layered structure consisting of two or more walls, with a plurality of ribs formed in the multi-layered structure of the sidewall to form a plurality of cavities in the structure of the sidewall, and a plurality of hollow portions defined inside the wall of said multi-layered sidewall.
In the plastic product, a communication hole may be formed at each of said ribs to allow the cavities to communicate with each other. In addition, an air suction valve and an air exhaust valve may be set in the sidewall so as to suck or exhaust air into or from the cavities in response to an expansion or contraction of the cavities.
The plastic product of this invention may be designed to be used in place of a conventional double-layered or triple-layered glass panel, or used as a structural beam, a window frame, or a door panel having openings for holding a window glass frame and accomplishing a ventilation effect. When necessary, the plastic product having a multi-layered sidewall structure may be formed of a transparent plastic material so as to accomplish a desired light transmitting effect higher than that of a conventional resin film or a conventional pair glass, and so the product of this invention may be preferably used as a material for greenhouses. The plastic product of this invention is sufficiently low to effectively prevent heat loss, and is high in its heat radiation effect, thus having high thermal efficiency and a high thermal insulation effect. This product is not expensive, and so it does not force a user to pay excessive money to buy it. Another advantage of this product resides in that it is usable almost permanently.
In the product of this invention, filler, such as urethane foam, may be injected into the cavities of the structural body to be integrated with the sidewall and the ribs of the body.
As The cavities of the structural body may be filled with a filler during an extrusion forming process, it is possible to produce a plastic product having the filler injected into the cavities being opened at both end portions and welded at inner surface of the cavities.
Since it is possible to produce a variety of plastic products having a flat panel shape, a corrugated panel shape, a boat shape, a channel shape, a tubular shape, a door panel shape, or an oil tank shape, the products of this invention may be usable in a variety of industrial fields.
The present invention also provides a method of forming a plastic product, comprising the steps of: extruding a plastic structural body having one or more cavities from a manifold of an extrusion head; continuously feeding the structural body to a mold-forming unit to seat the structural body in the mold-forming unit, and perforating a plurality of holes on the sidewall of the structural body using a plurality of perforating and injecting units of the mold-forming unit; and blowing the structural body by injecting hot air into the structural body and/or injection-molding the structural body by injecting a melted plastic material into the structural body at the mold-forming unit, thus producing a desired plastic product having one or more sealed cavities inside its completely sealed and continuous sidewall.
In the method, a rib thickness-adjusting unit may be installed at the manifold of the extrusion head so as to form a communication hole at each rib inside said structural body when the structural body is extruded from the manifold. After the extrusion molding process, the structural body is continuously fed to the mold-forming unit, and is subject to the hole forming process, the blow-molding process and/or the injection-molding process, and so the desired plastic product having the sealed cavities inside its completely sealed and continuous sidewall is produced.
In another embodiment of the present invention, the structural body is subject to the blow molding process and/or the injection-molding process at the mold-forming unit, and is also subject to a filling step of injecting a filler into said cavities through the hole made by said hole forming process using a perforating and injecting unit at the mold-forming unit, thus having the completely sealed and continuous sidewall with the sealed cavities filled and integrated with said filler.
In a further embodiment, the structural body is seated in the mold-forming unit provided with a movable core, and is subject to the hole forming process, the blow molding process, the injection-molding process and/or the filling process at the mold-forming unit, and so the structural body has the completely sealed and continuous sidewall with the sealed cavities filled and integrated with said filler.
In still another embodiment, the plastic forming method produces a desired plastic product by extruding a plastic structural body having one or more cavities in its sidewall, injecting a filler from a filler supply unit into the cavities through an injection pipe, thus integrating the filler with the sidewall and the ribs of the body, and seating the body in a mold-forming unit so as to perform an injection-molding process capable of forming sealed end walls of the structural body.
In a detailed description, the plastic forming method comprises the steps of: extruding a plastic structural body from the manifold of an extrusion molding unit, with one or more cavities formed inside the sidewall of said structural body; injecting hot air into the cavities of the body through a hot air injection pipe connected to the manifold, thus expanding the structural body; cutting the both end portions of the structural body after feeding the expanded structural body from the manifold to a mold-forming unit; forming one or more holes on the sidewall of the structural body using one or more perforating and injecting units provided at the mold-forming unit; injecting hot fluid into the cavities of the body, thus blowing the body; injecting low temperature air into the cavities of the body using the perforating and injecting units, and spraying low temperature air to the interior or exterior of the mold-forming unit by an air spraying unit, thus cooling the structural body; and ejecting the structural body from the mold-forming unit, whereby a desired plastic product having one or more sealed cavities inside its completely sealed sidewall is produced.
The present invention also provides a device for forming a plastic product, comprising: an extrusion molding unit used for extruding a plastic structural body having one or more cavities inside its sidewall; an injection pipe connected to the extrusion head of said extrusion molding unit, and used for injecting hot air into the cavities of the structural body to expand the structural body; a mold-forming unit installed to seat and mold the structural body fed from said extrusion molding unit; a plurality of perforating and injecting units provided at the mold-forming unit for forming a plurality of holes on the sidewall of the structural body, and injecting hot air into the cavities of the structural body to expand the structural body, and injecting a filler into the cavities of the structural body; and a feeding unit used for feeding the structural body from the extrusion molding unit to the mold-forming unit, whereby the device continuously performs one or more processes selected from an extrusion molding process, a blow molding process, a mold-forming process and a filling process, thus producing a desired plastic product having one or more sealed cavities inside its completely sealed and continuous sidewall.
In the present invention, a manifold is installed at the extrusion-molding unit, thus primarily extruding the desired plastic structural body having one or more cavities inside its sidewall. Thereafter, hot air is injected into the cavities of the structural body to expand the structural body. The expanded body is fed from the extrusion-molding unit to the mold-forming unit while maintaining its expanded shape. At the mold-forming unit, hot air is injected into the body to perform a blow molding process. In addition, a melted plastic material may be injected into the cavity of the top and bottom molds of the mold-forming unit, thus performing an injection molding process when necessary. A core may be installed at the mold-forming unit to form a shape on the structural body by the forming part of the core when necessary. Therefore, it is possible to produce a desired plastic product having one or more sealed cavities inside its completely sealed and continuous sidewall.
In the present invention, the plastic forming process cools the plastic product through an air-cooling process in place of a conventional water-cooling process at the mold-forming unit. Of course, it should be understood that it is possible to cool a specific part of the top and bottom molds using a conventional cooling liquid. The air-cooling process may be accomplished through a natural air cooling process or using an air spray nozzle installed at a desired area to spray highly pressurized air.
The plastic forming process of this invention using hot air or cool air for heating or cooling the plastic structural body is very different from the conventional extrusion molding processes or the conventional injection molding processes using water for cooling the products.
The plastic forming process of this invention effectively produces a plastic product, which is completely sealed at its six walls and has sealed cavities, with filler integrated with the structural body into a single structure. It is impossible for the conventional forming process to produce such a plastic product. Of course, it is impossible for the conventional forming process to produce a plastic product of this invention filled with filler, such as urethane, in the cavities sealed at its four walls and opened at both end portions. In the prior art, it is impossible to produce a plastic product, filled with such a filler in its cavities, in commercial quantities through an extrusion molding process since the conventional extrusion molding process primarily cools the product using water, and finally cools the product within a cooling tank while slightly elongating the product after a sizing process. Therefore, it is well known to those skilled in the art that the method and device for forming such plastic products is newly proposed and very effectively usable.
In the conventional extrusion molding process, the shape and size of a product is determined by a dice mold before the product passes through a water tank to be cooled. Such a conventional extrusion molding process can produce a single-layered panel or a single-layered pipe, but is not used for filling filler, such as urethane foam, in the cavity of the product due to a limit caused by the use of the dice mold and the water-cooling process. However, in the present invention, the plastic structural body extruded from the manifold of an extrusion-molding unit is directly seated in the cavity of a variety of molds without passing through a dice mold or a water tank. In the present invention, hot air and cool air may be preferably injected or sprayed to the mold-forming unit when necessary to adjust the production rate of the products.
In the present invention, a rib thickness adjusting plate or a rib thickness adjusting member are hinged to the manifold such that it is open able as desired to form a communication hole at each rob of the structural body. Due to the communication holes, the cavities communicate with each other, thus allowing the structural body to be fed from the extrusion-molding unit to the mold-forming unit while maintaining the uniformly expanded shape. This also allows the structural body to be uniformly formed during the blow molding process or the filling process performed at the mold-forming unit.
In the present invention, the communication holes are easily formed at the ribs of the structural body, and the shape and size of the resulting product is determined within the mold-forming unit designed to cool the product through an air-cooling process in place of a conventional water-cooling process. In the process of this invention, hot air is injected into the structural body inside the mold-forming unit by the perforating and injecting units installed at the mold-forming unit, thus finally expanding the body prior to feeding cool air to the body so as to quickly cooling the body. The process and device of this invention thus effectively produces a variety of desired plastic products, including panel-type or pipe-type products, or products filled with urethane foam as filler.
In addition, the rib thickness-adjusting unit installed at the manifold of the extrusion-molding unit is usable for controlling the thickness of the ribs as desired, in addition to forming the communication holes at the ribs. This rib thickness-adjusting unit is particularly usable for forming a beam-type or column-type plastic product having a specifically designed appearance.
The perforating and injecting unit installed at the mold-forming unit is commonly usable for forming the holes on the sidewall of the structural body, injecting hot air into the body, or injecting filler into the body as desired.
The plastic product of the present invention also has an air suction valve and an air exhaust valve on its sidewall to perform respiration through the valves in response to thermal expansion or contraction of a sealed cavity inside the sidewall, thus being protected from undesired deformation or breakage according to the variation of atmospheric temperature. This allows the product to be usable almost permanently, and so the present invention preferably conserves natural resources, in addition to preventing environmental pollution.
The plastic product of the panel type completely sealed at its six walls according to the present invention is preferably usable as a material for greenhouses, in place of conventional single-pair glass panels or double-pair glass panels. In the case of a plastic product having a two- or multi-layered cavity structure, a communication hole is formed at each rib to allow the cavities arranged in each layer to communicate with each other. In such a case, the cavities in the upper and lower layers do not communicate with each other since no hole is formed at the wall between the upper and lower cavities. Therefore, it is possible to further improve the thermal insulation effect of the plastic product. In the present invention, it is preferred to form the communication holes at the ribs such that the holes are misaligned from each other to reinforce the structural strength of the ribs, in addition to allowing air and filler to uniformly fill the cavities.
The plastic product of the panel type sealed at its six walls and filled with a filler, such as urethane foam, in the cavities defined within the walls according to the present invention has high thermal insulation effect, high buoyancy and high structural strength, in addition to effectively resisting corrosion, thus being preferably usable as an interior or exterior material of buildings. This product is also effectively usable for a desired lengthy period of time.
The plastic forming method and device of this invention particularly and easily produces a simple plastic product, which is sealed at its four walls and opened at its both end portions, and is filled with a filler, such as urethane foam, in its cavities, through a simple process.